The AGN unified model says every active galactic nucleus is the same object — a supermassive black hole with an accretion disk, a broad-line region (BLR) close in, a dusty obscuring torus further out, and (in radio-loud sources) a pair of relativistic jets along the spin axis. What we call it depends only on the angle θ between our line of sight and that axis:
θ < θ_o (torus doesn't block the core) → Type 1 (Seyfert 1 / Quasar): broad + narrow lines
θ ≥ θ_o (torus blocks the BLR) → Type 2 (Seyfert 2 / Radio Galaxy): narrow lines only, N_H high
If the source is radio-loud and a jet happens to point within a few degrees of us, relativistic beaming dominates everything else and we call it a blazar. Beaming strength is the Doppler factor:
δ = 1 / [γ(1 − β·cosθ)], β = √(1 − 1/γ²)
F_observed / F_rest = δ^(3+α) (continuous jet, spectral index α ≈ 0.7)
Small θ and large γ make δ ≫ 1 → enormous apparent brightness and even apparent superluminal motion for the approaching jet, while the receding counter-jet (angle 180°−θ) gets deboosted toward invisibility — exactly why blazar jets look one-sided.
- Orbit the 3D view — your camera's polar angle to the vertical jet axis becomes θ live; watch the classification flip as you cross θo.
- Torus opening angle — a wider torus (bigger θo) means more sightlines see an unobscured Type 1 nucleus.
- Lorentz factor γ & jets — raise γ and look nearly down the jet to watch the Doppler factor and flux boost spike, and the far jet fade.
- Eddington ratio — sets disk luminosity; a high-Eddington unobscured source reads as a quasar rather than a modest Seyfert 1.
Real observational evidence: the M87 and Sgr A* Event Horizon Telescope images, the Seyfert 1/2 dichotomy explained by torus inclination (Antonucci & Miller 1985 polarized broad lines in a Type 2), and blazar flares (Mrk 421, 3C 279) showing apparent faster-than-light jet-knot motion — a direct signature of δ ≫ 1.